Laterally excited bulk wave device with acoustic mirrors

ABSTRACT

A laterally excited bulk acoustic wave device is disclosed. The laterally excited bulk acoustic wave device can include a first solid acoustic mirror, a second solid acoustic mirror, a piezoelectric layer that is positioned between the first solid acoustic mirror and the second solid acoustic mirror, an interdigital transducer electrode on the piezoelectric layer, and a support substrate arranged to dissipate heat associated with the bulk acoustic wave. The interdigital transducer electrode is arranged to laterally excite a bulk acoustic wave. The first solid acoustic mirror and the second solid acoustic mirror are arranged to confine acoustic energy of the bulk acoustic wave. The first solid acoustic mirror is positioned on the support substrate.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication, including U.S. Provisional Patent Application No.62/943,092, filed Dec. 3, 2019, titled “LATERALLY EXCITED BULK WAVEDEVICE WITH ACOUSTIC MIRRORS,” are hereby incorporated by referenceunder 37 CFR 1.57 in their entirety.

BACKGROUND Technical Field

Embodiments of this disclosure relate to acoustic wave devices.

Description of Related Technology

An acoustic wave filter can include a plurality of resonators arrangedto filter a radio frequency signal. Example acoustic wave filtersinclude surface acoustic wave (SAW) filters and bulk acoustic wave (BAW)filters. A surface acoustic wave resonator can include an interdigitaltransductor electrode on a piezoelectric substrate. The surface acousticwave resonator can generate a surface acoustic wave on a surface of thepiezoelectric layer on which the interdigital transductor electrode isdisposed. In BAW resonators, acoustic waves propagate in a bulk of apiezoelectric layer. Example BAW resonators include film bulk acousticwave resonators (FBARs) and solidly mounted resonators (SMRs). Certainacoustic resonators can include features of SAW resonators and featuresof BAW resonators.

Acoustic wave filters can be implemented in radio frequency electronicsystems. For instance, filters in a radio frequency front end of amobile phone can include acoustic wave filters. An acoustic wave filtercan be a band pass filter. A plurality of acoustic wave filters can bearranged as a multiplexer. For example, two acoustic wave filters can bearranged as a duplexer. As another example, four acoustic wave filterscan be arranged as a quadplexer.

SUMMARY

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

In one embodiment, a laterally excited bulk acoustic wave device isdisclosed. The laterally excited bulk acoustic wave device can include afirst solid acoustic mirror, a second solid acoustic mirror, apiezoelectric layer positioned between the first solid acoustic mirrorand the second solid acoustic mirror, an interdigital transducerelectrode on the piezoelectric layer, and a support substrate arrangedto dissipate heat associated with the bulk acoustic wave. Theinterdigital transducer electrode is arranged to laterally excite a bulkacoustic wave. The first solid acoustic mirror and the second solidacoustic mirror are arranged to confine acoustic energy of the bulkacoustic wave. The first solid acoustic mirror is positioned on thesupport substrate.

In one embodiment, the laterally excited bulk acoustic wave devicefurther includes a second substrate that is configured to dissipate heatassociated with the bulk acoustic wave. The first solid acoustic mirrorand the second solid acoustic mirror both can be positioned between thesupport substrate and the second substrate.

In one embodiment, the first solid acoustic mirror is arranged toconfine acoustic energy such that the support substrate is free fromacoustic energy during operation of the laterally excited bulk acousticwave device.

In one embodiment, the first solid acoustic mirror is an acoustic Braggreflector that includes alternating low impedance and high impedancelayers. At least one of the low impedance layers and at least one of thehigh impedance layers can be free from acoustic energy during operationof the laterally excited bulk acoustic wave device. The high impedancelayers can each have a thickness in a range from about 0.14λ_(p) to0.30λ_(p) or from about 0.35λ_(p) to 0.45λ_(p), in which λ_(p) is a wavelength of longitudinal wave velocity.

In one embodiment, the support substrate is a silicon substrate.

In one embodiment, the piezoelectric layer has a thickness in a rangefrom 0.2 micrometers to 0.4 micrometers.

In one embodiment, the piezoelectric layer has a thickness in a rangefrom 0.2 micrometers to 0.3 micrometers.

In one embodiment, the piezoelectric layer is an aluminum nitride layer.

In one embodiment, the piezoelectric layer is a lithium niobate layer.

In one embodiment, the piezoelectric layer is a lithium tantalate layer.

In one embodiment, the laterally exited bulk acoustic wave device has aresonant frequency in a range from 4.5 gigahertz to 10 gigahertz.

In one embodiment, the laterally exited bulk acoustic wave device has aresonant frequency in a range from 5 gigahertz to 10 gigahertz.

In one embodiment, the laterally exited bulk acoustic wave device has aresonant frequency in a range from 10 gigahertz to 25 gigahertz.

In one embodiment, the laterally exited bulk acoustic wave device has aresonant frequency in a range from 3 gigahertz to 5 gigahertz.

In one aspect, a laterally excited bulk acoustic wave device isdisclosed. The laterally excited bulk acoustic wave device can include apiezoelectric layer and an interdigital transducer electrode on thepiezoelectric layer. The interdigital transducer electrode is configuredto laterally excite a bulk acoustic wave. The laterally excited bulkacoustic wave device can also include a pair of solid acoustic mirrorson opposing sides of the piezoelectric layer. The pair of solid acousticmirrors are configured to confine acoustic energy of the bulk acousticwave. The laterally excited bulk acoustic wave device can furtherinclude a support substrate. One solid acoustic mirror of the pair ofsolid acoustic mirrors is positions between the support substrate andthe piezoelectric layer.

In one embodiment, the laterally excited bulk acoustic wave devicefurther includes one or more suitable features disclosed herein.

In one aspect, a laterally excited bulk acoustic wave component isdisclosed. The laterally excited bulk acoustic wave component caninclude a first substrate, a first solid acoustic mirror on the firstsubstrate, a piezoelectric layer on the first solid acoustic mirror, andan interdigital transducer electrode on the piezoelectric layer. Theinterdigital transducer electrode that is arranged to laterally excite abulk acoustic wave. The laterally excited bulk acoustic wave componentcan also include a second solid acoustic mirror on the piezoelectriclayer and the interdigital transducer electrode. The first solidacoustic mirror and the second solid acoustic mirror are togetherarranged to confine acoustic energy of the bulk acoustic wave. Thelaterally excited bulk acoustic wave component can further include asecond substrate on the second solid acoustic mirror. The first andsecond solid acoustic mirrors are positioned between the first andsecond substrates. The first and second substrates are arranged todissipate heat associated with the bulk acoustic wave.

In one embodiment, the laterally excited bulk acoustic wave componentfurther includes a conductive via extending through the secondsubstrate. The conductive via can be electrically connected to alaterally excited bulk acoustic wave resonator that includes theinterdigital transducer electrode. The laterally excited bulk acousticwave component can further include an input/output contact that iselectrically connected to the conductive via.

In one embodiment, the laterally excited bulk acoustic wave componentfurther includes a third solid acoustic mirror on the second substrate,a second piezoelectric layer on the third solid acoustic mirror, and asecond interdigital transducer electrode on the second piezoelectriclayer. The laterally excited bulk acoustic wave component can furtherinclude an adhesion layer positioned between the second substrate andthe third solid acoustic mirror. The laterally excited bulk acousticwave component can further include a fourth solid acoustic mirror overthe second piezoelectric layer. The laterally excited bulk acoustic wavecomponent can further include a third substrate over the fourth solidacoustic mirror. The laterally excited bulk acoustic wave component canfurther include a third substrate over the second interdigitaltransducer electrode.

In one embodiment, the laterally excited bulk acoustic wave componentfurther includes circuitry on the second substrate. The circuitry caninclude a transistor. The circuitry can include a passive impedanceelement. The circuitry can include an acoustic wave device.

In one embodiment, the second substrate is a silicon substrate.

In one embodiment, the laterally excited bulk acoustic wave componentcan further include one or more suitable features disclosed herein.

In one aspect, a stacked acoustic wave device assembly is disclosed. Thestacked acoustic wave device assembly can include a first supportsubstrate and a first laterally excited bulk acoustic wave stack on thefirst support substrate. The first laterally excited bulk acoustic wavestack includes a first piezoelectric layer, a first interdigitaltransducer electrode on the first piezoelectric layer, and a pair ofsolid acoustic mirrors on opposing sides of the first piezoelectriclayer. The stacked acoustic wave device assembly can further include asecond support substrate positioned on the first laterally excited bulkacoustic wave stack, and a second laterally excited bulk acoustic wavestack on the second support substrate. The second laterally excited bulkacoustic wave stack includes a second piezoelectric layer, a secondinterdigital transducer electrode on the second piezoelectric layer, anda solid acoustic mirror positioned between the second piezoelectriclayer and the second support substrate.

In one embodiment, the solid acoustic mirror is included in a secondpair of solid acoustic mirrors. The second pair of solid acousticmirrors can be on opposing sides of the second piezoelectric layer.

In one embodiment, the stacked acoustic wave device assembly furtherincludes a third substrate over the second laterally excited bulkacoustic wave stack.

In one embodiment, the stacked acoustic wave device assembly furtherinclude an adhesion layer positioned between the second supportsubstrate and the solid acoustic mirror.

In one embodiment, the first laterally excited bulk acoustic wave stackand the second laterally excited bulk acoustic wave stack are includedin a single acoustic wave filter arranged to filter a radio frequencysignal.

In one embodiment, the first laterally excited bulk acoustic wave stackand the second laterally excited bulk acoustic wave stack are includedin different acoustic wave filters. The different acoustic wave filterscan be included in a multiplexer.

In one embodiment, the first piezoelectric layer has a thickness in arange from 0.2 micrometers to 0.4 micrometers.

In one embodiment, the first piezoelectric layer has a thickness in arange from 0.2 micrometers to 0.3 micrometers.

In one embodiment, the laterally exited bulk acoustic wave stack isincluded in a resonator having a resonant frequency in a range from 4.5gigahertz to 10 gigahertz.

In one embodiment, the laterally exited bulk acoustic wave stack isincluded in a resonator having a resonant frequency in a range from 5gigahertz to 10 gigahertz. The laterally exited bulk acoustic wave stackincluded in a resonator can have a resonant frequency in a range from 10gigahertz to 25 gigahertz.

In one embodiment, the stacked acoustic wave device assembly furtherincludes one or more suitable features disclosed herein.

In one aspect, an acoustic wave filter is disclosed. The acoustic wavefilter can include a laterally excited bulk acoustic wave resonator thatincludes a first solid acoustic mirror on a first substrate, apiezoelectric layer on the first solid acoustic mirror, an interdigitaltransducer electrode on the piezoelectric layer, and a second solidacoustic mirror on the piezoelectric layer and the interdigitaltransducer electrode. The acoustic wave filter can also include aplurality of acoustic wave resonators. The laterally excited bulkacoustic wave resonator and the plurality of acoustic wave resonatorsare together configured to filter a radio frequency signal.

In one embodiment, the acoustic wave filter is a band pass filter.

In one embodiment, the plurality of acoustic wave resonators include asecond laterally excited bulk acoustic wave resonator. The secondlaterally excited bulk acoustic wave resonator can include a third solidacoustic mirror on a second substrate, a second piezoelectric layer onthe third solid acoustic mirror, and a second interdigital transducerelectrode on the second piezoelectric layer. The second laterallyexcited bulk acoustic wave resonator can further include a fourth solidacoustic mirror on the second piezoelectric layer and the secondinterdigital transducer electrode. The second substrate can bepositioned between the second solid acoustic mirror and the third solidacoustic mirror. An adhesion layer can be positioned between the secondsubstrate and the third solid acoustic mirror.

In one embodiment, the laterally excited bulk acoustic wave resonatorhas a resonant frequency in a range from 4.5 gigahertz to 10 gigahertz.

In one embodiment, the laterally excited bulk acoustic wave resonatorhas a resonant frequency in a range from 5 gigahertz to 10 gigahertz.

In one embodiment, the laterally excited bulk acoustic wave resonatorhas a resonant frequency in a range from 10 gigahertz to 25 gigahertz.

In one embodiment, the piezoelectric layer has a thickness in a rangefrom 0.2 micrometers to 0.4 micrometers.

In one embodiment, the piezoelectric layer has a thickness in a rangefrom 0.2 micrometers to 0.3 micrometers.

In one embodiment, the acoustic wave filter further includes one or moresuitable features disclosed herein.

In one aspect, a radio frequency module is disclosed. The radiofrequency module can include any acoustic wave filter disclosed hereinand a radio frequency circuit element that is coupled to the acousticwave filter. The acoustic wave filter and the radio frequency circuitelement can be enclosed within a common package.

In one embodiment, the radio frequency circuit element is a radiofrequency amplifier arranged to amplify a radio frequency signal. Theradio frequency amplifier can be a low noise amplifier. The radiofrequency amplifier can be a power amplifier. The radio frequency modulecan further includes a switch that is configured to selectively couple aterminal of the acoustic wave filter to an antenna port of the radiofrequency module.

In one embodiment, the radio frequency circuit element is a switch thatis configured to selectively couple the acoustic wave filter to anantenna port of the radio frequency module.

In one aspect, a wireless communication device is disclosed. Thewireless communication device can include an acoustic wave filterdisclosed herein, an antenna that is operatively coupled to the acousticwave filter, a radio frequency amplifier that is operatively coupled tothe acoustic wave filter and configured to amplify a radio frequencysignal, and a transceiver that is in communication with the radiofrequency amplifier.

In one embodiment, the wireless communication device further includes abaseband processor that is in communication with the transceiver.

In one embodiment, the acoustic wave filter is included in a radiofrequency front end.

In one embodiment, the acoustic wave filter is included in a diversityreceive module.

In one aspect, a method of filtering a radio frequency signal isdisclosed. The method can include receiving a radio frequency signal ata port of an acoustic wave filter disclosed herein, and filtering theradio frequency signal with the acoustic wave filter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1A is cross sectional diagram of a laterally excited bulk acousticwave device according to an embodiment.

FIG. 1B is a plan view of an interdigital transducer (IDT) electrode ofthe laterally excited bulk acoustic wave device of FIG. 1A.

FIG. 2A is a cross sectional diagram of a laterally excited bulkacoustic wave device with a solid acoustic mirror according to anembodiment.

FIG. 2B is a cross sectional view showing heat flow in the laterallyexcited bulk acoustic wave device of FIG. 2A.

FIG. 3 is a cross sectional diagram of a baseline laterally excited bulkacoustic wave device.

FIG. 4A is graph of admittance of the baseline laterally excited bulkacoustic wave device of FIG. 3 .

FIG. 4B illustrates displacement at a resonant frequency for thebaseline laterally excited bulk acoustic wave device of FIG. 3 .

FIG. 4C illustrates displacement at an anti-resonant frequency for thebaseline laterally excited bulk acoustic wave device of FIG. 3 .

FIG. 5 is a cross sectional diagram of a laterally excited bulk acousticwave device with a support substrate in contact with a piezoelectriclayer.

FIG. 6A is graph of admittance of the laterally excited bulk acousticwave device of FIG. 5 .

FIG. 6B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 5 .

FIG. 6C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 5 .

FIG. 7 is a cross sectional diagram of a laterally excited bulk acousticwave device with a solid acoustic mirror according to an embodimentbefore design refinement.

FIG. 8A is graph of admittance of the laterally excited bulk acousticwave device of FIG. 7 .

FIG. 8B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 7 .

FIG. 8C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 7 .

FIG. 9 is a cross sectional diagram of a laterally excited bulk acousticwave device with a solid acoustic mirror according to an embodiment.

FIG. 10A is graph of admittance of the laterally excited bulk acousticwave device of FIG. 9 .

FIG. 10B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 9 .

FIG. 10C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 9 .

FIG. 10D is a graph corresponding to different thicknesses of thepiezoelectric layer for the laterally excited bulk acoustic wave deviceof FIG. 9 .

FIG. 10E is a graph corresponding to different thicknesses of theinterdigital transducer electrode for the laterally excited bulkacoustic wave device of FIG. 9 .

FIG. 10F is a cross sectional diagram of a laterally excited bulkacoustic wave device with a solid acoustic mirror and silicon dioxidebetween interdigital transducer electrode fingers according to anembodiment.

FIG. 10G is a graph corresponding to different thicknesses of theinterdigital transducer electrode for the laterally excited bulkacoustic wave device of FIG. 10F.

FIG. 11A is a cross sectional diagram of a laterally excited bulkacoustic wave device with a double solid acoustic mirror structureaccording to an embodiment.

FIG. 11B is a cross sectional view showing heat flow in the laterallyexcited bulk acoustic wave device of FIG. 11A.

FIG. 12A is graph of admittance of the laterally excited bulk acousticwave device with a double solid acoustic mirror structure of FIG. 11A.

FIG. 12B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device with a double solid acousticmirror structure of FIG. 11A.

FIG. 12C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device with a double solid acousticmirror structure of FIG. 11A.

FIG. 12D is a graph corresponding to different thicknesses of thepiezoelectric layer for the laterally excited bulk acoustic wave deviceof FIG. 11A.

FIG. 12E is a graph corresponding to different thicknesses of theinterdigital transducer electrode for the laterally excited bulkacoustic wave device of FIG. 11A.

FIG. 12F is a graph corresponding to different thicknesses of a lowimpedance layer of a solid acoustic mirror over the interdigitaltransducer electrode for the laterally excited bulk acoustic wave deviceof FIG. 11A.

FIG. 13 is a cross sectional diagram of an acoustic wave component witha laterally excited bulk acoustic wave device with a double solidacoustic mirror structure according to an embodiment.

FIG. 14 is a group comparing admittance of the laterally excited bulkacoustic wave devices of FIGS. 2A, 3, and 11A.

FIG. 15 illustrates a thermal simulation result of a laterally excitedbulk acoustic wave device with a membrane structure.

FIG. 16 illustrates a thermal simulation result of a laterally excitedbulk acoustic wave device with a single solid acoustic mirror structureaccording to an embodiment.

FIG. 17 illustrates a thermal simulation result of a laterally excitedbulk acoustic wave device with a double solid acoustic mirror structureaccording to an embodiment.

FIG. 18 is a cross sectional diagram of a stacked laterally excited bulkacoustic wave device structure according to an embodiment.

FIG. 19 is a cross sectional diagram of a stacked laterally excited bulkacoustic wave device structure according to another embodiment.

FIG. 20 is a cross sectional diagram of a stacked device structure witha laterally excited bulk acoustic wave device structure stacked withother circuitry according to another embodiment.

FIG. 21 is a schematic diagram of a ladder filter that includes alaterally excited bulk acoustic wave resonator according to anembodiment.

FIG. 22 is a schematic diagram of a lattice filter that includes alaterally excited bulk acoustic wave resonator according to anembodiment.

FIG. 23 is a schematic diagram of a hybrid ladder lattice filter thatincludes a laterally excited bulk acoustic wave resonator according toan embodiment.

FIG. 24A is a schematic diagram of an acoustic wave filter.

FIG. 24B is a schematic diagram of a duplexer.

FIG. 24C is a schematic diagram of a multiplexer with hard multiplexing.

FIG. 24D is a schematic diagram of a multiplexer with switchedmultiplexing.

FIG. 24E is a schematic diagram of a multiplexer with a combination ofhard multiplexing and switched multiplexing.

FIG. 25 is a schematic diagram of a radio frequency module that includesan acoustic wave filter according to an embodiment.

FIG. 26 is a schematic block diagram of a module that includes anantenna switch and duplexers according to an embodiment.

FIG. 27 is a schematic block diagram of a module that includes a poweramplifier, a radio frequency switch, and duplexers according to anembodiment.

FIG. 28 is a schematic block diagram of a module that includes a lownoise amplifier, a radio frequency switch, and filters according to anembodiment.

FIG. 29 is a schematic diagram of a radio frequency module that includesan acoustic wave filter according to an embodiment.

FIG. 30 is a schematic block diagram of a wireless communication devicethat includes a filter according to an embodiment.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following description of certain embodiments presents variousdescriptions of specific embodiments. However, the innovations describedherein can be embodied in a multitude of different ways, for example, asdefined and covered by the claims. In this description, reference ismade to the drawings where like reference numerals can indicateidentical or functionally similar elements. It will be understood thatelements illustrated in the figures are not necessarily drawn to scale.Moreover, it will be understood that certain embodiments can includemore elements than illustrated in a drawing and/or a subset of theelements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

Laterally excited bulk acoustic wave resonators can be include inacoustic wave filters for high frequency bands, such as frequency bandsabove 3 gigahertz (GHz) and/or frequency bands above 5 GHz. Suchfrequency bands can include a fifth generation (5G) New Radio (NR)operating band. Certain laterally excited bulk acoustic wave resonatorscan include an interdigital transducer (IDT) electrode on a relativelythin piezoelectric layer. A bulk acoustic wave (BAW) mode excited by theIDT electrode is not strongly affected by the pitch of IDT electrode incertain applications. Accordingly, such a resonator to have a higheroperating frequency than certain conventional surface acoustic wave(SAW) resonators. Certain laterally excited bulk acoustic waveresonators can be free standing. However, heat dissipation can beundesirable for such free standing laterally excited bulk acoustic waveresonators. Power durability and/or mechanical ruggedness of suchlaterally excited bulk acoustic wave resonators can be a technicalconcern. Free standing laterally excited bulk acoustic wave resonatorswith lithium niobate or lithium tantalate piezoelectric layers canencounter problems related to power durability in transmit filterapplications.

Heat dissipation and mechanical ruggedness can be improved by bonding apiezoelectric layer to a support substrate with a relatively highthermal conductivity. By bonding the piezoelectric layer directly to thesupport substrate, resonant characteristics can be degraded by leakageinto support substrate.

Aspects of this disclosure relate to a laterally excited bulk acousticwave resonator with a solid acoustic mirror positioned between apiezoelectric layer and a support substrate. An IDT electrode can bepositioned on the piezoelectric layer. The support substrate can have arelatively high thermal conductivity. For example, the support substratecan be a silicon support substrate. The solid acoustic mirror, which canbe an acoustic Bragg reflector, can reduce and/or eliminate leakage intothe support substrate. With such a structure, acoustic energy can beconfined over the solid acoustic mirror effectively and heat can flowthough the support substrate with the relatively high thermalconductivity. Mechanical ruggedness of such a laterally exited bulkacoustic wave resonator can be improved by avoiding an air cavity. Atthe same time, a relatively high frequency resonance can be achievedwith desirable power durability.

Aspects of this disclosure relate to a laterally excited bulk acousticwave resonator with a piezoelectric layer positioned between a doublesolid acoustic mirror structure on a support substrate. A secondsubstrate can be positioned on an opposite side of the double solidacoustic mirror structure than the support substrate. An IDT electrodecan be positioned on the piezoelectric layer. Such a laterally excitedbulk acoustic wave resonator can achieve desirable heat dissipation andmechanical ruggedness. At the same time, the laterally excited bulkacoustic wave resonator can achieve a relatively high frequencyresonance and desirable power durability. The package structure can alsobe less complex relative to a laterally excited bulk acoustic waveresonator with an air cavity.

A laterally excited bulk acoustic wave device including any suitablecombination of features disclosed herein be included in a filterarranged to filter a radio frequency signal in a fifth generation 5G NRoperating band within Frequency Range 1 (FR1). A filter arranged tofilter a radio frequency signal in a 5G NR operating band can includeone or more laterally excited bulk acoustic wave device disclosedherein. FR1 can be from 410 MHz to 7.125 GHz, for example, as specifiedin a current 5G NR specification.

A laterally excited bulk acoustic wave device disclosed herein can beincluded in a filter arranged to filter a radio frequency signal havinga frequency above FR1. For example, a laterally excited bulk acousticwave device can be included in a filter arranged to filter radiofrequency signals in a range from 10 GHz to 25 GHz. In applicationswhere such high frequency signals are being transmitted, higher transmitpowers can be used to account for higher loss in communication channelsat higher frequencies. Accordingly, thermal dissipation at highfrequencies of laterally excited bulk acoustic wave devices disclosedherein can be desirable.

In certain 5G applications, the thermal dissipation of the acoustic wavedisclosed herein can be advantageous. For example, such thermaldissipation can be desirable in 5G applications with a highertime-division duplexing (TDD) duty cycle compared to fourth generation(4G) Long Term Evolution (LTE) applications. As another example, therecan be more ganging of filters and carrier aggregation in 5Gapplications than 4G LTE applications. Accordingly, signals can havehigher power to account for losses associated with such ganging offilters and/or carrier aggregation. Thermal dissipation of laterallyexcited bulk acoustic wave devices disclosed can be implemented in theseexample applications to improve performance of filters.

One or more laterally excited bulk acoustic wave devices in accordancewith any suitable principles and advantages disclosed herein can beincluded in a filter arranged to filter a radio frequency signal in a 4GLTE operating band and/or in a filter having a passband that includes a4G LTE operating band and a 5G NR operating band.

FIG. 1A is cross sectional diagram of a laterally excited bulk acousticwave device 10 according to an embodiment. The laterally excited bulkacoustic wave device 10 can be a laterally excited bulk acoustic waveresonator included in a filter. The laterally excited bulk acoustic wavedevice 10 can be any other suitable laterally excited bulk acoustic wavedevice, such as a device in a delay line. The laterally excited bulkacoustic wave device 10 can be implemented in relatively high frequencyacoustic wave filters. Such acoustic wave filters can filter radiofrequency signals having a frequencies above 3 GHz and/over above 5 GHz.As illustrated, the laterally excited bulk acoustic wave device 10includes a piezoelectric layer 12, an IDT electrode 14, a first solidacoustic mirror 15, a second solid acoustic mirror 16, a first substrate17, and a second substrate 18. The solid acoustic mirrors 15 and 16 canconfine acoustic energy in the piezoelectric layer 12. The substrates 17and 18 can function like heat sinks. The substrates 17 and 18 canprovide thermal dissipation and improve power durability of thelaterally excited bulk acoustic wave device 10.

The piezoelectric layer 12 can be a lithium based piezoelectric layer.For example, the piezoelectric layer 12 can be a lithium niobate layer.As another example, the piezoelectric layer 12 can be a lithiumtantalate layer. In certain applications, the piezoelectric layer 12 canbe an aluminum nitride layer. The piezoelectric layer 12 can be anyother suitable piezoelectric layer.

In certain surface acoustic wave resonators, there can be horizontalacoustic wave propagation. In such surface acoustic wave resonators, IDTelectrode pitch can set the resonant frequency. Limitations ofphotolithography can set a lower bound on IDT electrode pitch and,consequently, resonant frequency of certain surface acoustic waveresonators.

The laterally excited bulk acoustic wave device 10 can generate a Lambwave that is laterally excited. A resonant frequency of the laterallyexcited bulk acoustic wave device 10 can depend on a thickness H1 of thepiezoelectric layer 12. The thickness H1 of the piezoelectric layer 12can be a dominant factor in determining the resonant frequency for thelaterally excited bulk acoustic wave device 10. The pitch of the IDTelectrode 14 can be a second order factor in determining resonantfrequency of the laterally excited bulk acoustic wave device 10. Athickness of a low impedance layer, such as a silicon dioxide layer,directly over the piezoelectric layer 12 and the IDT electrode and/ordirectly under the piezoelectric layer 12 can have a secondary impact onthe resonant frequency of the laterally excited bulk acoustic wavedevice 10. The thickness of such a low impedance layer can be sufficientto adjust resonant frequency for a shunt resonator and a seriesresonator of a filter.

The resonant frequency of the laterally excited bulk acoustic wavedevice 10 can be approximated based on Equations 1 and/or 2.

$\begin{matrix}{v = {f*\lambda}} & \left( {{Equation}\mspace{14mu} 1} \right) \\{f = \frac{v}{2\lambda}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$

In Equations 1 and 2, v can represent acoustic velocity in apiezoelectric material, f can represent resonant frequency, and λ canrepresent 2 times the thickness H1 of the piezoelectric layer 12.Accordingly, a combination of the thickness H1 of the piezoelectriclayer 12 and the acoustic velocity in the piezoelectric layer 12 candetermine the approximate resonant frequency of the laterally excitedbulk acoustic wave device 10. The resonant frequency can be increased bymaking the piezoelectric layer 12 thinner and/or by using apiezoelectric layer 12 with a higher acoustic velocity.

The piezoelectric layer 12 can be manufactured with a thickness H1 thatis 0.2 micrometers or higher from the fabrication point of view. Incertain applications, the piezoelectric layer can have a thicknessH1>0.04 L from the electrical performance (K²) point of view, in which Lis IDT electrode pitch.

The laterally excited bulk acoustic wave device 10 with a 0.2 micrometerthick aluminum nitride piezoelectric layer 12 can have a resonantfrequency of approximately 25 GHz based on Equations 1 and 2. Similarly,the laterally excited bulk acoustic wave device 10 with a 0.2 micrometerthick lithium niobate piezoelectric layer 12 can have a resonantfrequency of approximately 10 GHz. The laterally excited bulk acousticwave device 10 with a 0.4 micrometer thick lithium niobate piezoelectriclayer 12 can have a resonant frequency of approximately 5 GHz. Based onthe piezoelectric materials and thickness of the piezoelectric layer,the resonant frequency of the laterally excited bulk acoustic wavedevice 10 can be designed for filtering an RF signal having a particularfrequency.

Odd harmonics for a laterally excited bulk acoustic wave resonator canhave a k² that is sufficiently large for a ladder filter in certainapplications. Such odd harmonics (e.g., a 3^(rd) harmonic) can have a k²that is proportional to fundamental mode k². A laterally excited bulkacoustic wave resonator using an odd harmonic can have a lithium niobatepiezoelectric layer.

Filters that include one or more laterally excited bulk acoustic wavedevices 10 can filter radio frequency signals up to about 10 GHz with arelatively wide bandwidth. Filters that include one or more laterallyexcited bulk acoustic wave devices 10 can filter radio frequency signalshaving a frequency in a range from 10 GHz to 25 GHz. In some instances,a filter that include one or more laterally excited bulk acoustic wavedevices 10 can filter an RF signal having a frequency in a range from 3GHz to 5 GHz, a range from 4.5 GHz to 10 GHz, a range from 5 GHz to 10GHz, or a range from 10 GHz to 25 GHz.

In the laterally excited bulk acoustic wave device 10, the IDT electrode14 is over the piezoelectric layer 12. As illustrated, the IDT electrode14 has a first side in physical contact with the piezoelectric layer 12and a second side in physical contact with a layer of the solid acousticmirror 16. The IDT electrode 14 can include aluminum (Al), molybdenum(Mo), tungsten (W), gold (Au), silver (Ag), copper (Cu), platinum (Pt),ruthenium (Ru), titanium (Ti), the like, or any suitable combination oralloy thereof. The IDT electrode 14 can be a multi-layer IDT electrodein some applications.

The first solid acoustic mirror 15 includes alternating low impedancelayers 20A and high impedance layers 22A. Accordingly, the first solidacoustic mirror 15 is an acoustic Bragg reflector. The second solidacoustic mirror 16 includes alternating low impedance layers 20B andhigh impedance layers 22B. Accordingly, the second solid acoustic mirror16 is an acoustic Bragg reflector. The low impedance layers 20A and/or20B can be any suitable low impedance material such as silicon dioxide(SiO₂) or the like. The low impedance layers 20A and 20B can be the samematerial as each other in certain applications. The high impedancelayers 22A and/or 22B can be any suitable high impedance material suchas platinum (Pt), tungsten (W), iridium (Ir), aluminum nitride (AlN),molybdenum (Mo), or the like. The high impedance layers 22A and 22B canbe the same material as each other in certain applications.

As illustrated, the layer of the first solid acoustic mirror 15 closestto the piezoelectric layer 12 is a low impedance layer 20A. Having a lowimpedance layer 20A closest to the piezoelectric layer 12 can increasean electromechanical coupling coefficient (k²) of the laterally excitedbulk acoustic wave device 10 and/or bring a temperature coefficient offrequency (TCF) of the laterally excited bulk acoustic wave device 10closer to 0 in certain instances.

As illustrated, the layer of the first solid acoustic mirror 15 closestto the first substrate 17 is a high impedance layer 22A. Having a highimpedance layer 22A closest to the first substrate 17 can increasereflection of the layer of the first solid acoustic mirror 15 closest tothe first substrate 17. Alternatively, a solid acoustic mirror (notillustrated) with a low impedance layer 20A closest to the firstsubstrate 17 can have a higher adhesion with the first substrate 17. Forexample, when the first substrate 17 is a silicon substrate, the firstsubstrate should have a higher adhesion with a solid acoustic mirrorwith a silicon dioxide low impedance layer 20A that is closest to thesupport substrate (not illustrated) relative to the having a platinumhigh impedance layer 22A closest to the first substrate 17. A lowimpedance layer of an acoustic mirror in contact with the firstsubstrate 17 can have a reduced thickness compared to other lowimpedance layers of the acoustic mirror in certain applications.

As illustrated, the layer of the second solid acoustic mirror 16 closestto the piezoelectric layer 12 is a low impedance layer 20B. Having a lowimpedance layer 20B closest to the piezoelectric layer 12 can increasean electromechanical coupling coefficient of the laterally excited bulkacoustic wave device 10 and/or bring a TCF of the laterally excited bulkacoustic wave device 10 closer to 0 in certain instances.

As illustrated, the layer of the second solid acoustic mirror 16 closestto the second substrate 18 is a high impedance layer 22B. Having a highimpedance layer 22B closest to the second substrate 18 can increasereflection of the layer of the second solid acoustic mirror 16 closestto the second substrate 18. Alternatively, a solid acoustic mirror (notillustrated) with a low impedance layer 20B closest to the secondsubstrate 18 can have a higher adhesion with the first substrate 18. Alow impedance layer of an acoustic mirror in contact with the secondsubstrate 18 can have a reduced thickness compared to other lowimpedance layers of the acoustic mirror in certain applications.

The first substrate 17 can be any suitable support substrate. The firstsubstrate 17 can have a relatively high thermal conductivity todissipate heat associated with operation of the laterally excited bulkacoustic wave device 10. The first substrate 17 can be a siliconsubstrate. The first substrate 17 being a silicon substrate can beadvantageous for processing during manufacture of the laterally excitedbulk acoustic wave device 10 and provide desirable thermal conductivity.Silicon is also a relatively inexpensive material. The first substrate17 can be an aluminum nitride substrate. In some other applications, thefirst substrate 17 can be a quartz substrate, a ceramic substrate, aglass substrate, a spinel substrate, a magnesium oxide spinel substrate,a sapphire substrate, a diamond substrate, a diamond like carbonsubstrate, a silicon carbide substrate, a silicon nitride substrate, orthe like.

The second substrate 18 can be any suitable substrate. The secondsubstrate 18 can have a relatively high thermal conductivity todissipate heat associated with operation of the laterally excited bulkacoustic wave device 10. The second substrate 18 can be a siliconsubstrate. The second substrate 18 can be an aluminum nitride substrate.In some other applications, the second substrate 18 can be a quartzsubstrate, a ceramic substrate, a glass substrate, a spinel substrate, amagnesium oxide spinel substrate, a sapphire substrate, a diamondsubstrate, a diamond like carbon substrate, a silicon carbide substrate,a silicon nitride substrate, or the like.

In certain instances, the first substrate 17 and the second substrate 18can have similar thicknesses to account for thermal expansion. The firstsubstrate 17 and the second substrate 18 can be of the same material incertain applications.

FIG. 1B illustrates the IDT electrode 14 of the laterally excited bulkacoustic wave device 10 of FIG. 1A in plan view. Only the IDT electrode14 of the laterally excited bulk acoustic wave device 10 is shown inFIG. 1B. The IDT electrode 14 includes a bus bar 24 and IDT fingers 26extending from the bus bar 24. The IDT fingers 26 have a pitch of λ. Asdiscussed above, the pitch λ can have less impact than the thickness ofthe piezoelectric layer 12 in the laterally excited bulk acoustic wavedevice 10. The laterally excited bulk acoustic wave device 10 caninclude any suitable number of IDT fingers 26.

FIG. 2A is a cross sectional diagram of a laterally excited bulkacoustic wave device 28 with a solid acoustic mirror 15 according to anembodiment. The laterally excited bulk acoustic wave device 28 can be alaterally excited bulk acoustic wave resonator included in a filter. Thelaterally excited bulk acoustic wave device 28 can be any other suitablelaterally excited bulk acoustic wave device, such as a device in a delayline. FIG. 2A illustrates that a single solid acoustic mirror 15 can beimplemented in certain applications. As illustrated, the laterallyexcited bulk acoustic wave device 28 includes a support substrate 17, asolid acoustic mirror 15 on the support substrate 17, a piezoelectriclayer 12 on the solid acoustic mirror 15, and an IDT electrode 14 on thepiezoelectric layer 12. The IDT electrode 14 is arranged to laterallyexcite a bulk acoustic wave.

The piezoelectric layer 12 can have a thickness in a range from 0.2micrometers to 0.4 micrometers in certain applications. Thepiezoelectric layer can have a thickness in a range from 0.2 micrometersto 0.3 micrometers.

The solid acoustic mirror 15 can confine acoustic energy. The solidacoustic mirror 15 can confine acoustic energy such that the supportsubstrate 17 is free from acoustic energy during operation of thelaterally excited bulk acoustic wave device 28. At least one of the lowimpedance layers 20 and/or at least one of the high impedance layers 22can be free from acoustic energy during operation of the laterallyexcited bulk acoustic wave device 28.

The support substrate 17 can dissipate heat associated with generating alaterally excited bulk acoustic wave. The support substrate 17 has athermal conductivity that is higher than a thermal conductivity of thepiezoelectric layer 12. The support substrate 17 can be a siliconsubstrate.

Filters that include one or more laterally excited bulk acoustic wavedevices 28 can filter an RF signal having a frequency in a range from 3GHz to 5 GHz, a range from 4.5 GHz to 10 GHz, a range from 5 GHz to 10GHz, or a range from 10 GHz to 25 GHz.

FIG. 2B is a cross sectional view showing heat flow in the laterallyexcited bulk acoustic wave device 28 of FIG. 2A. During operation, heatcan be generated by the IDT electrode 14. This heat can flow through thepiezoelectric layer 12 and the solid acoustic mirror 15 to the substrate17. Accordingly, the solid acoustic mirror 15 can provide a heat flowpath from the piezoelectric layer 12 to the substrate 17. The substrate17 can have a relatively high thermal conductivity and provide heatdissipation. The substrate 17 can increase mechanical durability.

FIG. 3 is a cross sectional diagram of a baseline laterally excited bulkacoustic wave device 30. As illustrated, the baseline laterally excitedbulk acoustic wave device 30 includes a piezoelectric layer 12 and anIDT electrode 14 on the piezoelectric layer 12. The laterally excitedbulk acoustic wave device 30 can be a free standing device supportedover a support substrate. There can be an air cavity positioned betweenthe piezoelectric layer 12 and the support substrate.

FIG. 4A is graph of admittance of the baseline laterally excited bulkacoustic wave device 30 of FIG. 3 . This graph shows a relatively cleanfrequency response with a resonant frequency at around 4.8 GHz and ananti-resonant frequency around 5.4 GHz.

FIG. 4B illustrates displacement at a resonant frequency for thebaseline laterally excited bulk acoustic wave device 30 of FIG. 3 . FIG.4B indicates displacement in the piezoelectric layer 12 at the resonantfrequency.

FIG. 4C illustrates displacement at an anti-resonant frequency for thebaseline laterally excited bulk acoustic wave device 30 of FIG. 3 . FIG.4C indicates displacement in the piezoelectric layer 12 at theanti-resonant frequency.

FIG. 5 is a cross sectional diagram of a laterally excited bulk acousticwave device 50 with a support substrate in contact with a piezoelectriclayer. As illustrated, the laterally excited bulk acoustic wave device50 includes a piezoelectric layer 12, an IDT electrode 14 on a firstside of the piezoelectric layer 12, and a support substrate 17 incontact with a second side of the piezoelectric layer 12 that isopposite to the first side. The support substrate 17 can be a siliconsubstrate. The support substrate 17 can dissipate heat associated withoperation of the laterally excited bulk acoustic wave device 50.

FIG. 6A is graph of admittance of the laterally excited bulk acousticwave device 50 of FIG. 5 , in which the support substrate 17 is asilicon substrate. This graph indicates that the laterally excited bulkacoustic wave device 50 produces a low quality factor (Q) that isgenerally undesirable for an acoustic wave filter.

FIG. 6B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device 50 of FIG. 5 , in which thesupport substrate 17 is a silicon substrate. FIG. 6B indicates acousticenergy leakage into the silicon substrate at the resonant frequency.

FIG. 6C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device 50 of FIG. 5 , in which thesupport substrate 17 is a silicon substrate. FIG. 6B indicates acousticenergy leakage into the silicon substrate at the anti-resonantfrequency.

FIG. 7 is a cross sectional diagram of a laterally excited bulk acousticwave device 70 with a solid acoustic mirror according to an embodimentbefore design refinement and/or optimization. The laterally excited bulkacoustic wave device 70 includes a piezoelectric layer 12, aninterdigital transducer electrode 14 on the piezoelectric layer 12, asolid acoustic mirror 15 including alternating low impedance layers 20and high impedance layers 22, and a support substrate 17. The solidacoustic mirror 15 is positioned between the support substrate 17 andthe piezoelectric layer 12. The solid acoustic mirror 15 is notoptimized in the laterally excited bulk acoustic wave device 70. In FIG.7 , the support substrate 17 is not necessarily shown to scale. Thesupport substrate 17 can be the thickest element illustrated in thelaterally excited bulk acoustic wave device 70.

In the simulations for FIGS. 8A to 8C, the acoustic mirror includessilicon dioxide low impedance layers having a thickness of 0.1λ andplatinum (Pt) high impedance layers having a thickness of 0.1λ. Theperformance of the laterally excited bulk acoustic wave device 70 inthese simulations is degraded. This can be due to the high impedancelayers having a thickness that is away from range that leads to betterperformance.

FIG. 8A is graph of admittance of the laterally excited bulk acousticwave device 70 of FIG. 7 . This graph shows a generally undesirablefrequency response.

FIG. 8B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device 70 of FIG. 7 . FIG. 8Bindicates some acoustic energy leakage into the middle layers of thesolid acoustic mirror 15 at the resonant frequency.

FIG. 8C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device 70 of FIG. 7 . FIG. 8Cindicates acoustic energy leakage into the middle and lower layers ofthe solid acoustic mirror 15 at the anti-resonant frequency.

FIG. 9 is a cross sectional diagram of a laterally excited bulk acousticwave device 90 with a solid acoustic mirror according to an embodiment.The laterally excited bulk acoustic wave device 90 is like the laterallyexcited bulk acoustic wave device 70 of FIG. 7 , except that thelaterally excited bulk acoustic wave device 90 is modified to increaseconfinement of acoustic energy and produce a cleaner frequency response.In FIG. 9 , the support substrate 17 is not necessarily shown to scale.The support substrate 17 can be the thickest element illustrated in thelaterally excited bulk acoustic wave device 90.

The piezoelectric layer 12 can have a thickness to increase performanceof the laterally excited bulk acoustic wave device 90. For example, thepiezoelectric layer 12 can have a thickness in a range from about 0.04λto 0.5λ, in which λ is IDT electrode pitch. As one example, thepiezoelectric layer 12 can have a thickness of about 0.08λ.

The layers of the solid acoustic mirror 15 can each have a thickness toincrease performance of the laterally excited bulk acoustic wave device90. For example, the low impedance layers 20 can be silicon dioxidelayers having a thickness in a range from 0.02λ to 0.10λ. The highimpedance layers can be platinum layers having a thickness in a rangefrom 0.01λ to 0.03λ or 0.04λ to 0.06λ. As one example, the low impedancelayers 20 and high impedance layers 22 can each have a thickness ofabout 0.05λ. Preferred mirror layer thickness can vary for material. Forexample, in the case with high impedance layers that are tungsten,preferred thickness of the high impedance layer can be in a range from0.017λ to 0.027λ or from 0.049λ to 0.059λ. For molybdenum high impedancelayers, preferred thickness of each high impedance layer can be in arange from 0.040λ to 0.050λ or 0.010λ to 0.011λ. Normalized by wavelength of longitudinal wave velocity λ_(p) in each material, preferredlow impedance layer thickness for each silicon dioxide low impedancelayer can be in a range from 0.1λ_(p) to 0.3λ_(p) and each highimpedance layer thickness can be in a range from about 0.14λ_(p) to0.30λ_(p) or from about 0.35λ_(p) to 0.45λ_(p). In certain applications,the low impedance layers 20 and the high impedance layers 22 can havesimilar and/or approximately the same thicknesses. In some otherapplications, the low impedance layers 20 can have different thicknessthan the high impedance layers 22.

The simulations in FIGS. 10A to 10C correspond to a piezoelectric layerthickness of 0.08λ and low impedance and high impedance layers 20 and22, respectively, each having a thickness of 0.05λ.

FIG. 10A is graph of admittance of the laterally excited bulk acousticwave device of FIG. 9 . This graph shows a relatively clean frequencyresponse with a resonant frequency at around 4.6 GHz and ananti-resonant frequency around 5.0 GHz.

FIG. 10B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device FIG. 9 . FIG. 10B indicatesthat the acoustic energy in confined near the piezoelectric layer 12 atthe resonant frequency in the laterally excited bulk acoustic wavedevice 90. FIG. 10B shows improve acoustic energy confinement relativeto FIG. 8B.

FIG. 10C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 9 . FIG. 10Cindicates that the acoustic energy in confined near the piezoelectriclayer 12 at the anti-resonant frequency in the laterally excited bulkacoustic wave device 90. FIG. 10C shows improve acoustic energyconfinement relative to FIG. 8C.

FIG. 10D is a graph corresponding to different thicknesses of thepiezoelectric layer for the laterally excited bulk acoustic wave device90 of FIG. 9 . The different curves correspond to different thicknessesH1 for a lithium niobate piezoelectric layer 12. FIG. 10D indicates thatthe thickness H1 of the lithium niobate piezoelectric layer 12 can be atleast 0.06 L to achieve a preferred electrical performance (k²). Thethickness H1 of lithium niobate piezoelectric layer 12 can be at least200 nanometers from a fabrication point of view.

FIG. 10E is a graph corresponding to different thicknesses of theinterdigital transducer electrode for the laterally excited bulkacoustic wave device 90 of FIG. 9 . The different curves correspond todifferent thicknesses H2 for the IDT electrode 14. This graph indicatesthat an IDT electrode thickness H2 of greater than 0.02 L can excite aspurious mode. The simulations in FIG. 10E do not include the effect ofIDT electrode resistivity.

FIG. 10F is a cross sectional diagram of a laterally excited bulkacoustic wave device 100 with a solid acoustic mirror 15 and silicondioxide 102 between fingers of the IDT electrode 14 according to anembodiment. The laterally excited bulk acoustic wave device 100 is likethe laterally excited bulk acoustic wave device 90 of FIG. 9 , exceptthat silicon dioxide 102 is included between fingers of the IDTelectrode 14. In some other instances (not illustrated), silicon dioxideand/or another temperature compensation layer can cover fingers of theIDT electrode 14.

Including silicon dioxide 102 between fingers of the IDT electrode 14can suppress a spurious mode by thicker IDT electrodes. Resonantfrequency can be dominated by total thickness of the piezoelectric layer12 and silicon dioxide 102. An upper silicon dioxide layer (e.g., thesilicon dioxide 102) can provide frequency tuning. A trimming range canbe sufficient to cover series and parallel arms in a ladder type filter.

FIG. 10G is a graph corresponding to different thicknesses of the IDTelectrode 14 for the laterally excited bulk acoustic wave device 100 ofFIG. 10F. The simulations in FIG. 10G do not include the effect of IDTelectrode resistivity.

FIG. 11A is a cross sectional diagram of a laterally excited bulkacoustic wave device 110 with a double solid acoustic mirror structureaccording to an embodiment. With the double solid acoustic mirrorstructure, a more complex package structure can be avoided. Thelaterally excited bulk acoustic wave device 110 can includes a pair ofsolid acoustic mirrors including a first solid acoustic mirror 15 and asecond solid acoustic mirror 16, a piezoelectric layer 12 positionedbetween the first solid acoustic mirror 15 and the second solid acousticmirror 16, an IDT electrode 14 on the piezoelectric layer 12, a firstsubstrate 17 on which the first solid acoustic mirror 15 is positioned,and a second substrate 18 over the second solid acoustic mirror 16. TheIDT electrode 14 is arranged to laterally excite a bulk acoustic wave.The first solid acoustic mirror 15 and the second solid acoustic mirror16 are arranged to confine acoustic energy of the bulk acoustic wave.The first substrate 17 and the second substrate 18 are arranged todissipate heat associated with the bulk acoustic wave. The laterallyexcited bulk acoustic wave device 110 can perform as described withreference to FIGS. 1A and/or 1B.

FIG. 11B is a cross sectional view showing heat flow in the laterallyexcited bulk acoustic wave device 110 of FIG. 11A. During operation,heat can be generated by the IDT electrode 14. This heat can flowthrough the piezoelectric layer 12 and the first solid acoustic mirror15 to the first substrate 17. Accordingly, the first solid acousticmirror 15 can provide a heat flow path from the piezoelectric layer 12to the first substrate 17. The first substrate 17 can dissipate heat.Similarly, heat generated by the IDT electrode 14 can flow through thesecond solid acoustic mirror 16 to the second substrate 18. Accordingly,the second solid acoustic mirror 16 can provide a heat flow path fromthe IDT electrode 14 to the second substrate 18. The second substrate 18can dissipate heat. The first solid acoustic mirror 15 and the secondsolid acoustic mirror 16 can confine acoustic energy during operation.

FIG. 12A is graph of admittance of the laterally excited bulk acousticwave device 110 of FIG. 11A. This graph shows a desirable frequencyresponse. FIG. 12A indicates that the simulated laterally excited bulkacoustic wave device 110 has a resonant frequency at around 4.5 GHz andan anti-resonant frequency around 4.8 GHz.

FIG. 12B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device 110 of FIG. 11A. FIG. 12Bindicates that the acoustic energy in confined near the piezoelectriclayer 12 at the resonant frequency in the laterally excited bulkacoustic wave device 110.

FIG. 12C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device 110 of FIG. 11A. FIG. 12Cindicates that the acoustic energy in confined near the piezoelectriclayer 12 at the anti-resonant frequency in the laterally excited bulkacoustic wave device 110.

FIG. 12D is a graph corresponding to different thicknesses of thepiezoelectric layer for the laterally excited bulk acoustic wave device110 of FIG. 11A. The different curves correspond to differentthicknesses H1 for a lithium niobate piezoelectric layer 12. FIG. 12Dindicates that the thickness H1 of the lithium niobate piezoelectriclayer 12 can be at least 0.04 L to achieve a preferred electricalperformance (e.g., k²). The thickness H1 of lithium niobatepiezoelectric layer 12 can be at least 200 nanometers from a fabricationpoint of view.

FIG. 12E is a graph corresponding to different thicknesses of theinterdigital transducer electrode for the laterally excited bulkacoustic wave device 110 of FIG. 11A. The different curves correspond todifferent thicknesses H2 for the IDT electrode layer 14. In thelaterally excited bulk acoustic wave device 110, a low impedance layer(e.g., a silicon dioxide layer) overcoats the IDT electrode 14. This canmake the laterally excited bulk acoustic wave device 110 robust for IDTelectrode thickness H2. The simulations in FIG. 12E do not include theeffect of IDT electrode resistivity.

FIG. 12F is a graph corresponding to different thicknesses of a silicondioxide low impedance layer 20A of a solid acoustic mirror 16 over theinterdigital transducer electrode 14 for the laterally excited bulkacoustic wave device 110 of FIG. 11A. Height H3 of the low impedancelayer 20A in physical contact with the IDT electrode is varied for thedifferent curves in FIG. 12F. Frequency can be adjusted and/or trimmedby changing thickness H3 of the silicon dioxide low impedance layer 20Athat is in physical contact with the IDT electrode 14. A range forfrequency adjustment and/or trimming can be sufficient to cover seriesand parallel arms in a ladder type filter.

FIG. 13 is a cross sectional diagram of an acoustic wave component 130with a laterally excited bulk acoustic wave device with a double solidacoustic mirror structure according to an embodiment. The acoustic wavecomponent 130 can be referred to as a laterally excited bulk acousticwave component. The acoustic wave component 130 includes a firstsubstrate 17, a first solid acoustic mirror 15 on the first substrate17, a piezoelectric layer 12 on the first solid acoustic mirrorl5, anIDT electrode 14 on the piezoelectric layer 12, a second solid acousticmirror 16 on the piezoelectric layer 12 and the IDT electrode 14, and asecond substrate 18 on the second solid acoustic mirror 16. The acousticwave component 130 also includes input/output contacts 132 andconductive vias 134.

The input/output contacts 132 can be pins, for example. An input/outputcontact 132 can be electrically connected to one or more laterallyexcited bulk acoustic wave devices of the acoustic wave component by wayof a conductive via 134.

As illustrated, the conductive vias 134 extend through the secondsubstrate 18 and the second solid acoustic mirror 16. In some otherinstances (not illustrated), one or more conductive vias can extendthrough the first substrate 17. In such instances, there can be one ormore input/output contact on a side of the first substrate 17 oppositeto the piezoelectric layer that are electrically connected to the one ormore conductive vias.

The acoustic wave component 130 can include a plurality of laterallyexcited bulk acoustic wave resonators. For example, the acoustic wavecomponent 130 can include 10 to 20 laterally excited bulk acoustic waveresonators. The laterally excited bulk acoustic wave resonators of theacoustic wave component 130 can be included in a single filter or two ormore filters.

FIG. 14 is a group comparing admittance of the laterally excited bulkacoustic wave devices of FIGS. 2A, 3, and 11A. A relatively small amountof acoustic energy in a solid acoustic mirror or solid acoustic mirrorsduring operation of a laterally excited bulk acoustic wave device canreduce electromechanical coupling coefficient (k²). Theelectromechanical coupling coefficient can be proportional to thedifference between the resonant frequency and the anti-resonantfrequency of an acoustic resonator. FIG. 14 indicates that anelectromechanical coupling coefficient of about 20% can be achieved witha double mirror laterally exited bulk acoustic wave device. Thiselectromechanical coupling coefficient can still be desirable. Forexample, this electromechanical coupling coefficient can be higher thanfor temperature compensated surface acoustic wave resonators. The singlemirror laterally exited bulk acoustic wave device can achieve a higherelectromechanical coupling coefficient than the double mirror laterallyexited bulk acoustic wave device.

FIG. 15 illustrates a thermal simulation result of a laterally excitedbulk acoustic wave device with a membrane structure. The laterallyexcited bulk acoustic wave device with a membrane structure of FIG. 15includes a piezoelectric layer 12, an IDT electrode 14 on thepiezoelectric layer 12, an air cavity 152 under the piezoelectric layer12, and a support substrate 154. Although not shown in FIG. 15 , thesupport substrate 154 extends below the air cavity 154 such that the aircavity 152 is between a portion of the support substrate 154 and thepiezoelectric layer 12. The IDT electrode 14 generates heat duringoperation. This generated heat dissipates thought the relatively thinpiezoelectric layer 12 to the support substrate 154 laterally from theIDT electrode 14. This can cause the piezoelectric layer 12 to heat upto a high temperature. The piezoelectric layer 12 and the IDT electrode14 are hotter than the maximum value on the temperature scale in thethermal simulation. The thermal simulation indicates that the laterallyexcited bulk acoustic wave device with a membrane structure can heat upto about 124° C.

FIG. 16 illustrates a thermal simulation result of a laterally excitedbulk acoustic wave device with a single solid acoustic mirror structureaccording to an embodiment. The laterally excited bulk acoustic wavedevice with the single solid acoustic mirror structure is generallysimilar to the laterally excited bulk acoustic wave device 28 of FIGS.2A-2B and the laterally excited bulk acoustic wave device 90 of FIG. 9 .Heat can flow as illustrated in FIG. 2B. The IDT electrode 14 generatesheat during operation. The thermal simulation indicates that heat isdissipated into the support substrate 17. The highest temperature duringoperation can be at the IDT electrode 14. The thermal simulationindicates that the laterally excited bulk acoustic wave device with asingle solid acoustic mirror can heat up to about 37° C. This is asignificant improvement relative to the laterally excited bulk acousticwave device with a membrane structure of FIG. 15 .

FIG. 17 illustrates a thermal simulation result of a laterally excitedbulk acoustic wave device with a double solid acoustic mirror structureaccording to an embodiment. The laterally excited bulk acoustic wavedevices with the double solid acoustic mirror structure is generallysimilar to the laterally excited bulk acoustic wave device 10 of FIGS.1A-1B and the laterally excited bulk acoustic wave device 110 of FIGS.11A-11B. Heat can flow as illustrated in FIG. 11B. The IDT electrode 14generates heat during operation. Heat can be dissipated into supportsubstrates 17 and 18 on opposing sides of the IDT electrode 14. Thehighest temperature during operation can be at the IDT electrode 14. Thethermal simulation of indicates that the laterally excited bulk acousticwave device with the double solid acoustic mirror can heat up to about31° C. This is an improvement relative to the laterally excited bulkacoustic wave device with the single solid acoustic mirror of FIG. 16 .

FIG. 18 is a cross sectional diagram of a stacked laterally excited bulkacoustic wave device assembly 180 according to an embodiment. FIG. 18illustrates that laterally excited bulk acoustic wave devices can bestacked. The stacked laterally excited bulk acoustic wave deviceassembly 180 can implement a plurality of laterally excited bulkacoustic wave devices in a relatively small sized component. Such acomponent can have a relatively small vertical height and/or footprintfor implementing a plurality of acoustic wave devices.

As illustrated, the stacked laterally excited bulk acoustic wave deviceassembly 180 includes a first support substrate 17, a first laterallyexcited bulk acoustic wave stack on the first support substrate 17, asecond support substrate 18 positioned on the first laterally excitedbulk acoustic wave stack, a second laterally excited bulk acoustic wavestack on the second support substrate 18, and a third substrate 188.

The first laterally excited bulk acoustic wave stack includes a firstpiezoelectric layer 12, a IDT electrode 14 on the first piezoelectriclayer 12, and a first pair of solid acoustic mirrors on opposing sidesof the first piezoelectric layer 12. The first pair of solid acousticmirrors includes a first solid acoustic mirror 15 and a second solidacoustic mirror 16.

The second laterally excited bulk acoustic wave stack includes a secondpiezoelectric layer 182, a second IDT electrode 184 on the secondpiezoelectric layer 182, and a second pair of solid acoustic mirrors onopposing sides of the first piezoelectric layer 182. The second pair ofsecond solid acoustic mirrors includes a third solid acoustic mirror 185and a fourth solid acoustic mirror 186. The second piezoelectric layer182 can be implemented in accordance with any suitable principles andadvantages of the piezoelectric layers disclosed herein. The second IDTelectrode 184 can be implemented in accordance with any suitableprinciples and advantages of the IDT electrodes disclosed herein. Thesolid acoustic mirrors 185 and 186 include respective low impedancelayers 20C and 20D and respective high impedance layers 22C and 22D. Thesolid acoustic mirrors 185 and 186 can be implemented in accordance withany suitable principles and advantages of the solid acoustic mirrorsdisclosed herein. The third substrate 188 can be implemented inaccordance with any suitable principles and advantages of the substratesdisclosed herein.

In the stacked laterally excited bulk acoustic wave device assembly 180,the second support substrate 18 is implemented as a single supportsubstrate between solid acoustic mirrors of the laterally excited bulkacoustic wave stacks. The substrates 17, 18, and 188 can each includethe same material in certain applications. Two or more of the substrates17, 18, and 188 can include different materials in some otherapplications.

The stacked laterally excited bulk acoustic wave device assembly 180 caninclude devices of one or more filters arranged to filter RF signals.The first laterally excited bulk acoustic wave stack and the secondlaterally excited bulk acoustic wave stack can implement devices in thesame filter in certain applications. The first laterally excited bulkacoustic wave stack and the second laterally excited bulk acoustic wavestack can implement devices in different filter in various applications.In some such applications, the different filters can be included in amultiplexer.

Although two devices are stacked in FIG. 18 , three or more laterallyexcited bulk acoustic wave devices can be stacked in some otherapplications. Moreover, although two double mirror laterally excitedbulk acoustic devices are shown in FIG. 18 , a single mirror laterallyexcited bulk acoustic device can be stacked on a double mirror laterallyexcited bulk acoustic devices in some other applications.

FIG. 19 is a cross sectional diagram of a stacked laterally excited bulkacoustic wave device assembly 190 according to another embodiment. Withstacked structures, firm mechanical connections may not be needed.Accordingly, an adhesion layer can be implemented between layers. Thestacked laterally excited bulk acoustic wave device assembly 190 is likethe stacked laterally excited bulk acoustic wave device assembly 180 ofFIG. 18 , except that an adhesion layer 192 is included in the stackedlaterally excited bulk acoustic wave device assembly 190. The adhesionlayer 192 can be an epoxy layer. The adhesion layer 192 can be any othersuitable layer arranged to increase adhesion between the secondsubstrate 18 and the third solid acoustic mirror 185.

A laterally excited bulk acoustic wave can be stacked with othercircuitry. FIG. 20 is a cross sectional diagram of a stacked deviceassembly 200 with a laterally excited bulk acoustic wave device 110stacked with other circuitry 202 according to another embodiment. Asshown in FIG. 20 , other circuitry 202 can be implemented on the secondsubstrate 18. Implementing the other circuitry 202 on the secondsubstrate 18 can enable more integration of electrical components in amodule. This can reduce physical size of the module.

The second substrate 18 can be a semiconductor substrate. The secondsubstrate 18 can be a silicon substrate. A variety of other circuitry202 can be implemented on such a second substrate 18. The othercircuitry 202 can include one or more transistors, one or more passiveimpedance elements, one or more other acoustic wave devices, the like,or any suitable combination thereof.

For example, the other circuitry 202 can include one or moretransistors, such as one or more of a semiconductor-on-insulatortransistor, a silicon-on-insulator transistor, a complementary metaloxide semiconductor transistor, or the like.

Alternatively or additionally, the other circuitry can include one ormore passive impedance elements, such as one or more of a capacitor, aninductor, a resistor, a transformer, or a diode. In certain instances, afilter can include the laterally excited bulk acoustic wave device 110and an inductor capacitor circuit of the other circuitry.

As one more example, the other circuitry can include an acoustic wavedevice on the second substrate 18. Such an acoustic wave device, can asurface acoustic wave device such as a multi-layer piezoelectricsubstrate surface acoustic wave device, a bulk acoustic wave device suchas a film bulk acoustic wave resonator or s solidly mounted resonator, aboundary wave device, or the like. The laterally excited bulk acousticwave device 110 can be included in the same filter as the acoustic wavedevice of the other circuitry 202. Alternatively, the laterally excitedbulk acoustic wave device 110 can be included in a different filter asthe acoustic wave device of the other circuitry 202. The differentfilters can be included in a multiplexer in some instances.

One or more vias and/or other conductive structures (not shown) in thestacked device assembly 200 can provide an electrical connection betweenthe laterally excited bulk acoustic wave device 110 and the othercircuitry 202. Such electrical connections in the stacked deviceassembly 200 can reduce an impact of electrical connections between thelaterally excited bulk acoustic wave device 110.

Acoustic wave devices disclosed herein can be implemented in a varietyof different filter topologies. Example filter topologies includewithout limitation, ladder filters, lattice filters, hybrid ladderlattice filters, filters that include ladder stages and a multi-modesurface acoustic wave filter, and the like. Such filters can be bandpass filters. In some other applications, such filters include band stopfilters. In some instances, acoustic wave devices disclosed herein canbe implemented in filters with one or more other types of resonatorsand/or with passive impedance elements, such as one or more inductorsand/or one or more capacitors. Some example filter topologies will nowbe discussed with reference to FIGS. 21 to 23 . Any suitable combinationof features of the filter topologies of FIGS. 21 to 23 can beimplemented together with each other and/or with other filtertopologies.

FIG. 21 is a schematic diagram of a ladder filter 201 that includes alaterally excited bulk acoustic wave resonator according to anembodiment. The ladder filter 201 is an example topology that canimplement a band pass filter formed from acoustic wave resonators. In aband pass filter with a ladder filter topology, the shunt resonators canhave lower resonant frequencies than the series resonators. The ladderfilter 201 can be arranged to filter a radio frequency signal. Asillustrated, the ladder filter 201 includes series acoustic waveresonators R1 R3, R5, and R7 and shunt acoustic wave resonators R2, R4,R6, and R8 coupled between a first input/output port I/O₁ and a secondinput/output port 1/O₂. Any suitable number of series acoustic waveresonators can be included in a ladder filter. Any suitable number ofshunt acoustic wave resonators can be included in a ladder filter.

One or more of the acoustic wave resonators of the ladder filter 201 caninclude a laterally excited bulk acoustic wave filter according to anembodiment. In certain applications, all acoustic resonators of theladder filter 201 can be laterally excited bulk acoustic wave resonatorsin accordance with any suitable principles and advantages disclosedherein. According to some applications, the ladder filter 201 caninclude at least one laterally excited bulk acoustic wave deviceaccording to one embodiment and at least one other laterally excitedbulk acoustic wave device according to another embodiment.

The first input/output port I/O₁ can a transmit port and the secondinput/output port I/O₂ can be an antenna port. Alternatively, firstinput/output port I/O₁ can a receive port and the second input/outputport I/O₂ can be an antenna port.

FIG. 22 is a schematic diagram of a lattice filter 210 that includes alaterally excited bulk acoustic wave resonator according to anembodiment. The lattice filter 210 is an example topology of a band passfilter formed from acoustic wave resonators. The lattice filter 210 canbe arranged to filter an RF signal. As illustrated, the lattice filter210 includes acoustic wave resonators RL1, RL2, RL3, and RL4. Theacoustic wave resonators RL1 and RL2 are series resonators. The acousticwave resonators RL3 and RL4 are shunt resonators. The illustratedlattice filter 210 has a balanced input and a balanced output. One ormore of the illustrated acoustic wave resonators RL1 to RL4 can be alaterally excited bulk acoustic wave resonator in accordance with anysuitable principles and advantages disclosed herein.

FIG. 23 is a schematic diagram of a hybrid ladder and lattice filter 220that includes a laterally excited bulk acoustic wave resonator accordingto an embodiment. The illustrated hybrid ladder and lattice filter 220includes series acoustic resonators RL1, RL2, RH3, and RH4 and shuntacoustic resonators RL3, RL4, RH1, and RH2. The hybrid ladder andlattice filter 220 includes one or more laterally excited bulk acousticwave resonators in accordance with any suitable principles andadvantages disclosed herein. For example, the series resonators RL1,RL2, RH3, and RH4 and the shunt resonators RL3, RL4, RH1, and RH2 caneach be a laterally excited bulk acoustic wave resonator according to anembodiment.

According to certain applications, a laterally excited bulk acousticwave resonator can be included in filter that also includes one or moreinductors and one or more capacitors.

The laterally excited bulk acoustic wave resonators disclosed herein canbe implemented in a standalone filter and/or in a filter in any suitablemultiplexer. Such filters can be any suitable topology, such as anyfilter topology of FIGS. 21 to 23 . The filter can be a band pass filterarranged to filter a 4G LTE band and/or 5G NR band. Examples of astandalone filter and multiplexers will be discussed with reference toFIGS. 24A to 24E. Any suitable principles and advantages of thesefilters and/or multiplexers can be implemented together with each other.

FIG. 24A is schematic diagram of an acoustic wave filter 230. Theacoustic wave filter 230 is a band pass filter. The acoustic wave filter230 is arranged to filter a radio frequency. The acoustic wave filter230 includes one or more acoustic wave devices coupled between a firstinput/output port RF_IN and a second input/output port RF_OUT. Theacoustic wave filter 230 includes a laterally excited bulk acoustic waveresonator according to an embodiment.

FIG. 24B is a schematic diagram of a duplexer 232 that includes anacoustic wave filter according to an embodiment. The duplexer 232includes a first filter 230A and a second filter 230B coupled totogether at a common node COM. One of the filters of the duplexer 232can be a transmit filter and the other of the filters of the duplexer232 can be a receive filter. In some other instances, such as in adiversity receive application, the duplexer 232 can include two receivefilters. Alternatively, the duplexer 232 can include two transmitfilters. The common node COM can be an antenna node.

The first filter 230A is an acoustic wave filter arranged to filter aradio frequency signal. The first filter 230A includes one or moreacoustic wave resonators coupled between a first radio frequency nodeRF1 and the common node COM. The first radio frequency node RF1 can be atransmit node or a receive node. The first filter 230A includes alaterally excited bulk acoustic wave resonator in accordance with anysuitable principles and advantages disclosed herein.

The second filter 230B can be any suitable filter arranged to filter asecond radio frequency signal. The second filter 230B can be, forexample, an acoustic wave filter, an acoustic wave filter that includesa laterally exited bulk acoustic wave resonator, an LC filter, a hybridacoustic wave LC filter, or the like. The second filter 230B is coupledbetween a second radio frequency node RF2 and the common node. Thesecond radio frequency node RF2 can be a transmit node or a receive node

Although example embodiments may be discussed with filters or duplexersfor illustrative purposes, any suitable principles and advantagesdisclosed herein can be implement in a multiplexer that includes aplurality of filters coupled together at a common node. Examples ofmultiplexers include but are not limited to a duplexer with two filterscoupled together at a common node, a triplexer with three filterscoupled together at a common node, a quadplexer with four filterscoupled together at a common node, a hexaplexer with six filters coupledtogether at a common node, an octoplexer with eight filters coupledtogether at a common node, or the like. Multiplexers can include filtershaving different passbands. Multiplexers can include any suitable numberof transmit filters and any suitable number of receive filters. Forexample, a multiplexer can include all receive filters, all transmitfilters, or one or more transmit filters and one or more receivefilters. One or more filters of a multiplexer can include any suitablenumber of laterally excited bulk acoustic wave devices.

FIG. 24C is a schematic diagram of a multiplexer 234 that includes anacoustic wave filter according to an embodiment. The multiplexer 234includes a plurality of filters 230A to 230N coupled together at acommon node COM. The plurality of filters can include any suitablenumber of filters including, for example, 3 filters, 4 filters, 5filters, 6 filters, 7 filters, 8 filters, or more filters. Some or allof the plurality of acoustic wave filters can be acoustic wave filters.As illustrated, the filters 230A to 230N each have a fixed electricalconnection to the common node COM. This can be referred to as hardmultiplexing or fixed multiplexing. Filters have fixed electricalconnections to the common node in hard multiplexing applications.

The first filter 230A is an acoustic wave filter arranged to filter aradio frequency signal. The first filter 230A can include one or moreacoustic wave devices coupled between a first radio frequency node RF1and the common node COM. The first radio frequency node RF1 can be atransmit node or a receive node. The first filter 230A includes alaterally excited bulk acoustic wave resonator in accordance with anysuitable principles and advantages disclosed herein. The other filter(s)of the multiplexer 234 can include one or more acoustic wave filters,one or more acoustic wave filters that include a laterally excited bulkacoustic wave resonator, one or more LC filters, one or more hybridacoustic wave LC filters, or any suitable combination thereof.

FIG. 24D is a schematic diagram of a multiplexer 236 that includes anacoustic wave filter according to an embodiment. The multiplexer 236 islike the multiplexer 234 of FIG. 24C, except that the multiplexer 236implements switched multiplexing. In switched multiplexing, a filter iscoupled to a common node via a switch. In the multiplexer 236, theswitch 237A to 237N can selectively electrically connect respectivefilters 230A to 230N to the common node COM. For example, the switch237A can selectively electrically connect the first filter 230A thecommon node COM via the switch 237A. Any suitable number of the switches237A to 237N can electrically a respective filters 230A to 230N to thecommon node COM in a given state. Similarly, any suitable number of theswitches 237A to 237N can electrically isolate a respective filter 230Ato 230N to the common node COM in a given state. The functionality ofthe switches 237A to 237N can support various carrier aggregations.

FIG. 24E is a schematic diagram of a multiplexer 238 that includes anacoustic wave filter according to an embodiment. The multiplexer 238illustrates that a multiplexer can include any suitable combination ofhard multiplexed and switched multiplexed filters. One or more laterallyexcited bulk acoustic wave devices can be included in a filter that ishard multiplexed to the common node of a multiplexer. Alternatively oradditionally, one or more laterally excited bulk acoustic wave devicescan be included in a filter that is switch multiplexed to the commonnode of a multiplexer

The acoustic wave devices disclosed herein can be implemented in avariety of packaged modules. Some example packaged modules will now bedisclosed in which any suitable principles and advantages of theacoustic wave devices, acoustic wave components, or stacked acousticwave device assemblies disclosed herein can be implemented. The examplepackaged modules can include a package that encloses the illustratedcircuit elements. A module that includes a radio frequency component canbe referred to as a radio frequency module. The illustrated circuitelements can be disposed on a common packaging substrate. The packagingsubstrate can be a laminate substrate, for example. FIGS. 25 to 29 areschematic block diagrams of illustrative packaged modules according tocertain embodiments. Any suitable combination of features of thesepackaged modules can be implemented with each other. While duplexers areillustrated in the example packaged modules of FIGS. 26, 27, and 29 ,any other suitable multiplexer that includes a plurality of filterscoupled to a common node and/or standalone filter can be implementedinstead of one or more duplexers. For example, a quadplexer can beimplemented in certain applications. As another example, one or morefilters of a packaged module can be arranged as a transmit filter or areceive filter that is not included in a multiplexer.

FIG. 25 is a schematic diagram of a radio frequency module 240 thatincludes an acoustic wave component 242 according to an embodiment. Theillustrated radio frequency module 240 includes the acoustic wavecomponent 242 and other circuitry 243. The acoustic wave component 242can include one or more acoustic wave devices in accordance with anysuitable combination of features of the acoustic wave filters disclosedherein. The acoustic wave component 242 can include an acoustic wavefilter that includes a plurality of laterally excited bulk acoustic waveresonators, for example.

The acoustic wave component 242 shown in FIG. 25 includes one or moreacoustic wave devices 244 and terminals 245A and 245B. The one or moreacoustic wave devices 244 includes an acoustic wave device implementedin accordance with any suitable principles and advantages disclosedherein. The terminals 245A and 244B can serve, for example, as an inputcontact and an output contact. Although two terminals are illustrated,any suitable number of terminals can be implemented for a particularapplication. The acoustic wave component 242 and the other circuitry 243are on a common packaging substrate 246 in FIG. 25 . The packagesubstrate 246 can be a laminate substrate. The terminals 245A and 245Bcan be electrically connected to contacts 247A and 247B, respectively,on the packaging substrate 246 by way of electrical connectors 248A and248B, respectively. The electrical connectors 248A and 248B can be bumpsor wire bonds, for example.

The other circuitry 243 can include any suitable additional circuitry.For example, the other circuitry can include one or more radio frequencyamplifiers (e.g., one or more power amplifiers and/or one or more lownoise amplifiers), one or more radio frequency switches, one or moreadditional filters, one or more RF couplers, one or more delay lines,one or more phase shifters, the like, or any suitable combinationthereof. The other circuitry 243 can be electrically connected to theone or more acoustic wave devices 244. The radio frequency module 240can include one or more packaging structures to, for example, provideprotection and/or facilitate easier handling of the radio frequencymodule 240. Such a packaging structure can include an overmold structureformed over the packaging substrate 246. The overmold structure canencapsulate some or all of the components of the radio frequency module240.

FIG. 26 is a schematic block diagram of a module 250 that includesduplexers 251A to 251N and an antenna switch 252. One or more filters ofthe duplexers 251A to 251N can include an acoustic wave device inaccordance with any suitable principles and advantages disclosed herein.Any suitable number of duplexers 251A to 251N can be implemented. Theantenna switch 252 can have a number of throws corresponding to thenumber of duplexers 251A to 251N. The antenna switch 252 can include oneor more additional throws coupled to one or more filters external to themodule 250 and/or coupled to other circuitry. The antenna switch 252 canelectrically couple a selected duplexer to an antenna port of the module250.

FIG. 27 is a schematic block diagram of a module 260 that includes apower amplifier 262, a radio frequency switch 264, and duplexers 251A to251N according to an embodiment. The power amplifier 262 can amplify aradio frequency signal. The radio frequency switch 264 can be amulti-throw radio frequency switch. The radio frequency switch 264 canelectrically couple an output of the power amplifier 262 to a selectedtransmit filter of the duplexers 251A to 251N. One or more filters ofthe duplexers 251A to 251N can include an acoustic wave device inaccordance with any suitable principles and advantages disclosed herein.Any suitable number of duplexers 251A to 251N can be implemented.

FIG. 28 is a schematic block diagram of a module 270 that includesfilters 272A to 272N, a radio frequency switch 274, and a low noiseamplifier 276 according to an embodiment. One or more filters of thefilters 272A to 272N can include any suitable number of acoustic wavedevices in accordance with any suitable principles and advantagesdisclosed herein. Any suitable number of filters 272A to 272N can beimplemented. The illustrated filters 272A to 272N are receive filters.In some embodiments (not illustrated), one or more of the filters 272Ato 272N can be included in a multiplexer that also includes a transmitfilter. The radio frequency switch 274 can be a multi-throw radiofrequency switch. The radio frequency switch 274 can electrically couplean output of a selected filter of filters 272A to 272N to the low noiseamplifier 276. In some embodiments (not illustrated), a plurality of lownoise amplifiers can be implemented. The module 270 can includediversity receive features in certain applications.

FIG. 29 is a schematic diagram of a radio frequency module 280 thatincludes an acoustic wave filter according to an embodiment. Asillustrated, the radio frequency module 280 includes duplexers 251A to251N, a power amplifier 262, a select switch 264, and an antenna switch252. The radio frequency module 280 can include a package that enclosesthe illustrated elements. The illustrated elements can be disposed on acommon packaging substrate 287. The packaging substrate 287 can be alaminate substrate, for example. A radio frequency module that includesa power amplifier can be referred to as a power amplifier module. Aradio frequency module can include a subset of the elements illustratedin FIG. 29 and/or additional elements. The radio frequency module 280may include any one of the acoustic wave filters in accordance with anysuitable principles and advantages disclosed herein.

The duplexers 251A to 251N can each include two acoustic wave filterscoupled to a common node. For example, the two acoustic wave filters canbe a transmit filter and a receive filter. As illustrated, the transmitfilter and the receive filter can each be a band pass filter arranged tofilter a radio frequency signal. One or more of the transmit filters caninclude an acoustic wave device in accordance with any suitableprinciples and advantages disclosed herein. Similarly, one or more ofthe receive filters can include an acoustic wave device in accordancewith any suitable principles and advantages disclosed herein. AlthoughFIG. 29 illustrates duplexers, any suitable principles and advantagesdisclosed herein can be implemented in other multiplexers (e.g.,quadplexers, hexaplexers, octoplexers, etc.) and/or in switch-plexersand/or with standalone filters.

The power amplifier 262 can amplify a radio frequency signal. Theillustrated switch 264 is a multi-throw radio frequency switch. Theswitch 264 can electrically couple an output of the power amplifier 262to a selected transmit filter of the transmit filters of the duplexers251A to 251N. In some instances, the switch 264 can electrically connectthe output of the power amplifier 262 to more than one of the transmitfilters. The antenna switch 252 can selectively couple a signal from oneor more of the duplexers 251A to 251N to an antenna port ANT. Theduplexers 251A to 251N can be associated with different frequency bandsand/or different modes of operation (e.g., different power modes,different signaling modes, etc.).

The acoustic wave devices disclosed herein can be implemented inwireless communication devices. FIG. 30 is a schematic block diagram ofa wireless communication device 290 that includes a filter according toan embodiment. The wireless communication device 290 can be a mobiledevice. The wireless communication device 290 can be any suitablewireless communication device. For instance, a wireless communicationdevice 290 can be a mobile phone, such as a smart phone. As illustrated,the wireless communication device 290 includes a baseband system 291, atransceiver 292, a front end system 293, antennas 294, a powermanagement system 295, a memory 296, a user interface 297, and a battery298.

The wireless communication device 290 can be used communicate using awide variety of communications technologies, including, but not limitedto, 2G, 3G, 4G (including LTE, LTE-Advanced, and LTE-Advanced Pro), 5GNR, WLAN (for instance, WiFi), WPAN (for instance, Bluetooth andZigBee), WMAN (for instance, WiMax), and/or GPS technologies.

The transceiver 292 generates RF signals for transmission and processesincoming RF signals received from the antennas 294. Variousfunctionalities associated with the transmission and receiving of RFsignals can be achieved by one or more components that are collectivelyrepresented in FIG. 30 as the transceiver 292. In one example, separatecomponents (for instance, separate circuits or dies) can be provided forhandling certain types of RF signals.

The front end system 293 aids in conditioning signals transmitted toand/or received from the antennas 294. In the illustrated embodiment,the front end system 293 includes antenna tuning circuitry 300, poweramplifiers (PAs) 301, low noise amplifiers (LNAs) 302, filters 303,switches 304, and signal splitting/combining circuitry 305. However,other implementations are possible. The filters 303 can include one ormore acoustic wave filters that include any suitable number of laterallyexcited bulk acoustic wave devices in accordance with any suitableprinciples and advantages disclosed herein.

For example, the front end system 293 can provide a number offunctionalities, including, but not limited to, amplifying signals fortransmission, amplifying received signals, filtering signals, switchingbetween different bands, switching between different power modes,switching between transmission and receiving modes, duplexing ofsignals, multiplexing of signals, or any suitable combination thereof.

In certain implementations, the wireless communication device 290supports carrier aggregation, thereby providing flexibility to increasepeak data rates. Carrier aggregation can be used for Frequency DivisionDuplexing (FDD) and/or Time Division Duplexing (TDD), and may be used toaggregate a plurality of carriers and/or channels. Carrier aggregationincludes contiguous aggregation, in which contiguous carriers within thesame operating frequency band are aggregated. Carrier aggregation canalso be non-contiguous, and can include carriers separated in frequencywithin a common band or in different bands.

The antennas 294 can include antennas used for a wide variety of typesof communications. For example, the antennas 294 can include antennasfor transmitting and/or receiving signals associated with a wide varietyof frequencies and communications standards.

In certain implementations, the antennas 294 support MIMO communicationsand/or switched diversity communications. For example, MIMOcommunications use multiple antennas for communicating multiple datastreams over a single radio frequency channel. MIMO communicationsbenefit from higher signal to noise ratio, improved coding, and/orreduced signal interference due to spatial multiplexing differences ofthe radio environment. Switched diversity refers to communications inwhich a particular antenna is selected for operation at a particulartime. For example, a switch can be used to select a particular antennafrom a group of antennas based on a variety of factors, such as anobserved bit error rate and/or a signal strength indicator.

The wireless communication device 290 can operate with beamforming incertain implementations. For example, the front end system 293 caninclude amplifiers having controllable gain and phase shifters havingcontrollable phase to provide beam formation and directivity fortransmission and/or reception of signals using the antennas 294. Forexample, in the context of signal transmission, the amplitude and phasesof the transmit signals provided to the antennas 294 are controlled suchthat radiated signals from the antennas 294 combine using constructiveand destructive interference to generate an aggregate transmit signalexhibiting beam-like qualities with more signal strength propagating ina given direction. In the context of signal reception, the amplitude andphases are controlled such that more signal energy is received when thesignal is arriving to the antennas 294 from a particular direction. Incertain implementations, the antennas 294 include one or more arrays ofantenna elements to enhance beamforming.

The baseband system 291 is coupled to the user interface 297 tofacilitate processing of various user input and output (I/O), such asvoice and data. The baseband system 291 provides the transceiver 292with digital representations of transmit signals, which the transceiver292 processes to generate RF signals for transmission. The basebandsystem 291 also processes digital representations of received signalsprovided by the transceiver 292. As shown in FIG. 30 , the basebandsystem 291 is coupled to the memory 296 of facilitate operation of thewireless communication device 290.

The memory 296 can be used for a wide variety of purposes, such asstoring data and/or instructions to facilitate the operation of thewireless communication device 290 and/or to provide storage of userinformation.

The power management system 295 provides a number of power managementfunctions of the wireless communication device 290. In certainimplementations, the power management system 295 includes a PA supplycontrol circuit that controls the supply voltages of the poweramplifiers 301. For example, the power management system 295 can beconfigured to change the supply voltage(s) provided to one or more ofthe power amplifiers 301 to improve efficiency, such as power addedefficiency (PAE).

As shown in FIG. 30 , the power management system 295 receives a batteryvoltage from the battery 298. The battery 298 can be any suitablebattery for use in the wireless communication device 290, including, forexample, a lithium-ion battery.

Any of the embodiments described above can be implemented in associationwith mobile devices such as cellular handsets. The principles andadvantages of the embodiments can be used for any systems or apparatus,such as any uplink wireless communication device, that could benefitfrom any of the embodiments described herein. The teachings herein areapplicable to a variety of systems. Although this disclosure includesexample embodiments, the teachings described herein can be applied to avariety of structures. Any of the principles and advantages discussedherein can be implemented in association with RF circuits configured toprocess signals having a frequency in a range from about 30 kHz to 300GHz, such as in a frequency range from about 400 MHz to 25 GHz.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as packaged radio frequency modules, radiofrequency filter die, uplink wireless communication devices, wirelesscommunication infrastructure, electronic test equipment, etc. Examplesof the electronic devices can include, but are not limited to, a mobilephone such as a smart phone, a wearable computing device such as a smartwatch or an ear piece, a telephone, a television, a computer monitor, acomputer, a modem, a hand-held computer, a laptop computer, a tabletcomputer, a microwave, a refrigerator, a vehicular electronics systemsuch as an automotive electronics system, a robot such as an industrialrobot, an Internet of things device, a stereo system, a digital musicplayer, a radio, a camera such as a digital camera, a portable memorychip, a home appliance such as a washer or a dryer, a peripheral device,a wrist watch, a clock, etc. Further, the electronic devices can includeunfinished products.

Unless the context indicates otherwise, throughout the description andthe claims, the words “comprise,” “comprising,” “include,” “including”and the like are to generally be construed in an inclusive sense, asopposed to an exclusive or exhaustive sense; that is to say, in thesense of “including, but not limited to.” Conditional language usedherein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,”“for example,” “such as” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and/orstates. The word “coupled”, as generally used herein, refers to two ormore elements that may be either directly coupled, or coupled by way ofone or more intermediate elements. Likewise, the word “connected”, asgenerally used herein, refers to two or more elements that may be eitherdirectly connected, or connected by way of one or more intermediateelements. Additionally, the words “herein,” “above,” “below,” and wordsof similar import, when used in this application, shall refer to thisapplication as a whole and not to any particular portions of thisapplication. Where the context permits, words in the above DetailedDescription using the singular or plural number may also include theplural or singular number respectively.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel filters, multiplexer,devices, modules, wireless communication devices, apparatus, methods,and systems described herein may be embodied in a variety of otherforms. Furthermore, various omissions, substitutions and changes in theform of the filters, multiplexer, devices, modules, wirelesscommunication devices, apparatus, methods, and systems described hereinmay be made without departing from the spirit of the disclosure. Forexample, while blocks are presented in a given arrangement, alternativeembodiments may perform similar functionalities with differentcomponents and/or circuit topologies, and some blocks may be deleted,moved, added, subdivided, combined, and/or modified. Each of theseblocks may be implemented in a variety of different ways. Any suitablecombination of the elements and/or acts of the various embodimentsdescribed above can be combined to provide further embodiments. Theaccompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thedisclosure.

What is claimed is:
 1. A laterally excited bulk acoustic wave devicecomprising: a first solid acoustic mirror; a second solid acousticmirror; a piezoelectric layer positioned between the first solidacoustic mirror and the second solid acoustic mirror; an interdigitaltransducer electrode on the piezoelectric layer, the interdigitaltransducer electrode arranged to laterally excite a bulk acoustic wave,the first solid acoustic mirror and the second solid acoustic mirrorarranged to confine acoustic energy of the bulk acoustic wave; a supportsubstrate arranged to dissipate heat associated with the bulk acousticwave, the first solid acoustic mirror being positioned on the supportsubstrate; and a second substrate configured to dissipate heatassociated with the bulk acoustic wave, the first solid acoustic mirrorand the second solid acoustic mirror both being positioned between thesupport substrate and the second substrate.
 2. The laterally excitedbulk acoustic wave device of claim 1 wherein the first solid acousticmirror is an acoustic Bragg reflector that includes alternating lowimpedance and high impedance layers.
 3. The laterally excited bulkacoustic wave device of claim 2 wherein at least one of the lowimpedance layers and at least one of the high impedance layers are freefrom acoustic energy during operation of the laterally excited bulkacoustic wave device.
 4. The laterally excited bulk acoustic wave deviceof claim 2 wherein the high impedance layers each have a thickness in arange from about 0.14λ_(p) to 0.30λ_(p) or from about 0.35λ_(p) to0.45λ_(p), in which λ_(p) is a wave length of longitudinal wavevelocity.
 5. The laterally excited bulk acoustic wave device of claim 1wherein the first solid acoustic mirror is arranged to confine acousticenergy such that the support substrate is free from acoustic energyduring operation of the laterally excited bulk acoustic wave device. 6.The laterally excited bulk acoustic wave device of claim 1 wherein thelaterally exited bulk acoustic wave device has a resonant frequency in arange from 4.5 gigahertz to 10 gigahertz.
 7. The laterally excited bulkacoustic wave device of claim 1 wherein the laterally exited bulkacoustic wave device has a resonant frequency in a range from 10gigahertz to 25 gigahertz.
 8. The laterally excited bulk acoustic wavedevice of claim 1 wherein the piezoelectric layer is an aluminum nitridelayer.
 9. The laterally excited bulk acoustic wave device of claim 1wherein the piezoelectric layer is a lithium niobate layer or a lithiumtantalate layer.
 10. A stacked acoustic wave device assembly comprising:a first support substrate; a first laterally excited bulk acoustic wavestack on the first support substrate; the first laterally excited bulkacoustic wave stack including a first piezoelectric layer, a firstinterdigital transducer electrode on the first piezoelectric layer, anda pair of solid acoustic mirrors on opposing sides of the firstpiezoelectric layer; a second support substrate positioned on the firstlaterally excited bulk acoustic wave stack; and a second laterallyexcited bulk acoustic wave stack on the second support substrate, thesecond laterally excited bulk acoustic wave stack including a secondpiezoelectric layer, a second interdigital transducer electrode on thesecond piezoelectric layer, and a solid acoustic mirror positionedbetween the second piezoelectric layer and the second support substrate.11. The stacked acoustic wave device assembly of claim 10 wherein thesolid acoustic mirror is included in a second pair of solid acousticmirrors, the second pair of solid acoustic mirrors being on opposingsides of the second piezoelectric layer.
 12. The stacked acoustic wavedevice assembly of claim 10 further comprising a third substrate overthe second laterally excited bulk acoustic wave stack.
 13. The stackedacoustic wave device assembly of claim 10 further comprising an adhesionlayer positioned between the second support substrate and the solidacoustic mirror.
 14. The stacked acoustic wave device assembly of claim10 wherein the first laterally excited bulk acoustic wave stack and thesecond laterally excited bulk acoustic wave stack are included in asingle acoustic wave filter arranged to filter a radio frequency signal.15. The stacked acoustic wave device assembly of claim 10 wherein thefirst piezoelectric layer has a thickness in a range from 0.2micrometers to 0.4 micrometers.
 16. A laterally excited bulk acousticwave component comprising: a first substrate; a first solid acousticmirror on the first substrate; a piezoelectric layer on the first solidacoustic mirror; an interdigital transducer electrode on thepiezoelectric layer, the interdigital transducer electrode arranged tolaterally excite a bulk acoustic wave; a second solid acoustic mirror onthe piezoelectric layer and the interdigital transducer electrode, thefirst solid acoustic mirror and the second solid acoustic mirrortogether arranged to confine acoustic energy of the bulk acoustic wave;and a second substrate on the second solid acoustic mirror, the firstand second solid acoustic mirrors being positioned between the first andsecond substrates, the first and second substrates arranged to dissipateheat associated with the bulk acoustic wave.
 17. The laterally excitedbulk acoustic wave component of claim 16 further comprising a conductivevia extending through the second substrate, wherein the conductive viais electrically connected to a laterally excited bulk acoustic waveresonator that includes the interdigital transducer electrode.
 18. Thelaterally excited bulk acoustic wave component of claim 16 furthercomprising a third solid acoustic mirror on the second substrate, asecond piezoelectric layer on the third solid acoustic mirror, and asecond interdigital transducer electrode on the second piezoelectriclayer.
 19. A laterally excited bulk acoustic wave device comprising: afirst solid acoustic mirror; a second solid acoustic mirror; apiezoelectric layer positioned between the first solid acoustic mirrorand the second solid acoustic mirror, the piezoelectric layer having athickness in a range from 0.2 micrometers to 0.4 micrometers; aninterdigital transducer electrode on the piezoelectric layer, theinterdigital transducer electrode arranged to laterally excite a bulkacoustic wave, the first solid acoustic mirror and the second solidacoustic mirror arranged to confine acoustic energy of the bulk acousticwave; and a support substrate arranged to dissipate heat associated withthe bulk acoustic wave, the first solid acoustic mirror being positionedon the support substrate.
 20. The laterally excited bulk acoustic wavedevice of claim 19 wherein the piezoelectric layer is an aluminumnitride layer, a lithium niobate layer or a lithium tantalate layer, andthe laterally exited bulk acoustic wave device has a resonant frequencyin a range from 10 gigahertz to 25 gigahertz.